Tamper-proof odometer one-way drive



June 23, 1970 G. HACHTEL 3,516,603

TAMPER-PROOF ODOMETER ONE-WAY DRIVE Filed Aug. 2. 1968 INVENTOR.

Guemer Hachtel BY ATTORNEY United States fice Patented June 23, 1970 3,516,603 TAMPER-PROOF ODOMETER ONE-WAY DRIVE Guenter Hachtel, Swartz Creek, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Aug. 2, 1968, Ser. No. 749,798 Int. Cl. G01c 22/00; G06m 1/04 US. Cl. 235-95 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a drive mechanism for use on a counter having a number of wheels such as the counters commonly used on odometers wherein the drive mechanism drives the counter as well as prevents reversal of operation, by means of a gear and ratchet arrangement.

This invention relates to a drive mechanism for a counting device and, more specifically, to a counting device such as an odometer wherein the drive mechanism has a novel means of preventing reversal of the counting device or odometer.

This invention may be used on counting devices or odometers of the type shown and described in US. Pat. No. 3,137,444 wherein the components are basically similar but, in addition, include the drive mechanism of this invention which prevents the reversing or turning back of the numbered wheels on the counting device to show a lesser reading than that which was actually counted.

An object of the present invention is to provide a drive mechanism for a counter device such as an odometer which will disengage itself upon being operated in the reverse direction from that of its normal Operational direction, generally a clockwise direction.

These and other features of the invention will be readily apparent from the following specification and drawings wherein:

FIG. 1 is a perspective view of the drive mechanism separated from the counting or numbered wheels;

FIG. 2 is a sectional view looking in the direction of arrows 2-2 of FIG. 1 and showing the drive mechanism engaged;

FIG. 3 is a sectional view showing the drive mechanism disengaged;

FIG. 4 is an end view taken in the direction of arrows 4-4 of FIG. 2.

There is shown in FIG. 1 a counter device, such as an odometer 10, having a number of counting wheels 12, 14, in side-by-side relation and carrier or partition plates 16 between each wheel which serve to separate the counting wheels and, in addition, serve as carrier means for pinion gears which move the respective counting wheels. Notched tongue 18 used in conjunction with a fixed pin assures a non-rotative position of the carrier plates 16. US. Pat. No. 3,137,444 describes and shows the operation of the counting device and movement of the number wheels by means of the pinion and carrier plates.

Number wheel 14 is a decimal wheel representing the least significant digit and has formed on the interior circumference thereof inwardly projecting gear teeth 20. It is understood however that a single tooth may be used. Also formed on the interior of the decimal Wheel is a bushing or shaft means 22. Pawl, latch or directionally disengageable link member 24 having an elongated hole therein fits over bushing 22. Bushing 22 serves as a guide and bearing for operation of the link member and, in addition, aids in retaining pawl 24 adjacent number wheel 14. Link member 24 has a tab 28 thereon which rides in and follows a generally radially spiral cam groove 30 on disc-faced drive gear 32. The generally radially spiral cam groove 30 extends about about the axis of drive gear 32. In addition, there is formed on the link member a second drive tab or drive tang 34. Drive tab 34 mates with the internal gear teeth 20.

Drive gear 32 mates with shaft 36 and forms the end plate and the drive means for the counting device. Retaining washer 38, or similar retaining means, serves to retain the complete assembly in fixed relationship. As shown in the drawing, the toothed surface 20 on number wheel 14 is partially telescoped over the disc face of drive gear 32.

In operation, the counter or odometer is driven in the forward or clockwise direction by drive gear 32 and shaft 36. As shown in FIG. 2, the disengageable link member 24 is in a downward or drive position, wherein the drive tab 34 mates with one of the gear teeth 20 on decimal wheel 14 to drive the counter device or odometer in a forward or counting direction. As shown in FIG. 3, when drive gear 32 is reversed, tab 28 moves along cam groove 30 moving disengageable link member 24 radially upward to disengage the second drive tab 34 from mating engagement with gear teeth 20. This disengagement is accomplished by the movement of tab 28 in the generally radially spiral cam groove 30 an amount substantially equal to the total length of the groove formed on the disc-faced drive gear 32. With the drive tab disengaged, the number wheels will no longer be driven and will remain stationary.

The invention provides a means of preventing reversal of a counting device or odometer by use of a simple, easily assembled and manufactured pawl and drive gear having a novel cam arrangement, which novel features are more particularly set out in the appended claims.

What is claimed is as follows:

1. In a counting device, a drive member adapted to be rotated about an axis and defining a disc-like face having a radially spiral cam groove, a plurality of number wheels mounted in side-by-side relation coaxial with said drive member to indicate digitally a number representing the rotation of the drive member in a predetermined direction, the number wheel representing the least significant digit defining an internal toothed surface at least partially telescoped over the disc-like face of said drive member, a shaft means on said axis within the confines of said internal toothed surface, and a directionally disengageable link member telescoped over said shaft means with freedom of radial movement at least approximately equal to the variation in radial position of said groove, the

link member being composed of a generally planar member located in parallel adjacent relationship with said face, having an axially extending first tab portion extending into said spiral cam groove, and having a radially extending second tab portion adapted to engage the teeth of said toothed surface when the first tab portion is in the radially innermost portion of the groove and to be retracted out of engagement with said teeth when the first tab portion is in the radially outmost portion of the groove.

2. In a counting device, a drive member adapted to be rotated about an axis and defining a disc-like face having a radially spiral cam groove, a plurality of number wheels mounted in side-by-side relation coaxial with said drive member to indicate digitally a number representing the rotation of the drive member in a predetermined direction, the number wheel representing the least significant digit defining an internal surface at least partially telescoped over the disc-like face of said drive member and having at least one radially inwardly projecting shoulder and adapted to receive a tab to turn the wheel in said predetermined direction, a shaft means on said axis within the confines of said internal surface, and a directionally disengageable link member telescoped over said shaft means with freedom of radial movement at least substantially equal to the variation in radial position of said groove, the link member having a first tab portion extending into said spiral cam groove and a second tab portion adapted to engage said shoulder when the first tab portion is in the radially innermost portion of the groove and to be retracted out of engagement with said shoulder when the first tab portion is in the radially outermost portion of the groove.

3. In a counting device, a drive member adapted to be rotated about an axis and defining a disc-like face having a radially spiral cam groove, a plurality of number wheels mounted in side-'by-side relation coaxial with said drive member to indicate digitally a number representing the rotation of the drive member in a predetermined direction, the number wheel representing the least significant digit defining an internal surface at least partially telescoped over the disc-like face of said drive member and having at least one radially inwardly projecting shoulder and adapted to receive a tab to turn the wheel in said predetermined direction, and a directionally disengageable link member disposed adjacent said face with freedom of radial movement in relation to said axis at least substantially equal to the variation in radial position of said groove, the link member havin a first tab portion extending into said spiral cam groove and a second tab portion adapted to engage said shoulder when the first tab portion is in the radially innermost portion of the groove and to be retracted out of engagement with said shoulder when the first tab portion is in the radially outermost portion of the groove.

4. In a counting device, a drive member adapted to be rotated about an axis and defining a disc-like face having a radially spiral cam groove extending about 180", a plurality of number wheels mounted in side-byside relation coaxial with said drive member to indicate member in a predetermined direction, the number wheel representing the least significant digit defining an internal toothed surface at least partially telescoped over the disc-like face of said drive member, a shaft means on said axis within the confines of said internal toothed surface, and a directionally disengageable link member having an elongated central opening telescoped over the shaft means, the link member being composed of a generally planar member located in parallel adjacent relationship with said face, having an axially extending first tab portion extending into said spiral cam groove, and having a radially extending second tab portion adapted to engage the teeth of said toothed surface when the first tab portion is in the radially innermost portion of the groove and to be radially retracted out of engagement with said teeth when the first tab portion is in the radially outmost portion of the groove, the elongated central opening having its length dimension along a line extending substantially between the ends of the groove and the opening being of length to permit the radial movement of the link member.

References Cited UNITED STATES PATENTS 351,238 10/1886 Williams 192-46 710,593 10/1902 Medley 192-46 716,041 12/ 1902 Houghtaling 192-46 3,097,792 7/1963 Haraoa 235-95 X 3,200,918 8/1965 Horn 192-46 RICHARD B. WILKINSON, Primary Examiner S. A. WAL, Assistant Examiner US. Cl. X.R. 235-91 

